In different apparatuses that require compression of a working fluid, particularly, in domestic appliances that employ a refrigerating cycle, such as refrigerators, a load on the appliance actually varies at all times, to require variation of a compression capacity of the compressor according to the variation of the load for improvement of an operation efficiency. To meet such a capacity variation requirement of the compressor, there have been different technical attempts, such as a variable rotation speed compressor, a multi-cylinder compressor, and the like. However, the technologies have many problems in putting into practical use of the technologies because of cost, and/or increased size of the compressor, instead of which a reciprocating type dual capacity compressor is developed by employing a simple mechanical structure. That is, the dual capacity compressor actually has two different compression capacities in respective rotation directions, i.e., a regular rotation direction (clockwise direction) and a reverse rotation direction (counter clockwise direction) by means of reversible motor and crankshaft, and a stroke varying structure in a crank pin region, of which the most general form is disclosed in U.S. Pat. No. 4,236,874.
The dual capacity compressor in the U.S. Pat. No. 4,236,874 is provided with a piston in a cylinder, a crankshaft, a crank pin having a center eccentric from a center of the crankshaft, an eccentric ring coupled with the crank pin, a connecting rod coupled both with the eccentric ring and the piston. The eccentric ring, and the connecting rod are rotatable with respect to adjoining components centered on the center of the crank pin. There is a length of release region in each of contact surfaces of the crank pin and the eccentric ring, between which a key is provided for coupling the crank pin and the eccentric ring, together. By using such a structure, the crankshaft rotates in a clockwise direction (regular rotation direction) when a heavy load is required, and the crankshaft rotates in a counter clockwise direction (reverse rotation direction) when a light load is required. That is, states of an eccentric ring arrangement differ in respective rotation directions, which in turn vary the piston stroke, to provide maximum stroke Lmax and compression capacity in the regular rotation direction when the eccentricity is the greatest, and minimum stroke Lmin and compression capacity in the reverse rotation direction when the eccentricity is the smallest.
Since moving parts, such as the motor/crankshaft, the piston, and the connecting rod, move at comparatively high speeds, an appropriate lubrication, and a lubricating system for the appropriate lubrication are required for the moving parts commonly for smooth operation of the compressor. In the reciprocating type compressor, the lubricating oil is held in a bottom of the compressor, and the crankshaft moves the lubricating oil upward along an oil passage therein and supplies to required moving parts by a centrifugal force of the crankshaft and a viscosity of the lubricating oil itself. However, if a lubricating oil system of a related art reciprocating type compressor, in which a centrifugal force is utilized mostly, is applied to the dual capacity compressor, lubricating performances may be varied with the rotation directions. Accordingly, though a lubrication oil system optimized to respective rotation directions is actually required, the U.S. Pat. No. 4,236,874 fails to teach such a lubrication oil system.
In the meantime, other than the U.S. Pat. No. 4,236,874, there are many patents that disclose technologies related to the dual capacity compressor, which will be described, briefly.
Similarly, U.S. Pat. No. 4,479,419 discloses a dual capacity compressor that employs a crank pin, an eccentric cam, and a key. The key is fixed to the eccentric cam, and moves along a rail on the crank pin when a rotation direction of the compressor is changed.
Also, in a compressor disclosed in U.S. Pat. No. 5,951,261, a bore of a fixed inside diameter is formed in an eccentric part, and a bore with an inside diameter the same with the bore in the eccentric part is formed at one side of an eccentric cam. A pin is provided to the bore in the eccentric part, and a compression spring is provided to the bore in the eccentric cam, so that the pin moves into the bore in the cam by a centrifugal force when respective bores are aligned during rotation, for restriction of the eccentric part and the eccentric cam.
However, not only the foregoing patents, but also other related patents, disclose the stroke varying structure of the dual capacity compressor, but fail to disclose an appropriate lubricating oil system.